(1) Field of the Invention
The invention is related to a windshield wiper system for vehicles, particularly a windshield wiper system for rotary wing aircrafts as a helicopter.
(2) Description of Related Art
The cleaning performance of wiper blades depends on a lean angle (α) between a wiper blade axis (Y), which is perpendicular to the longitudinal extension of the wiper blade (l) and is going through the contact point of a lip of the wiper blade with the windshield outer surface and a perpendicular line (Y1) to the windshield outer surface at said same contact point.
The best cleaning performance of a wiper blade is provided when the wiper blade is perpendicular to the windshield surface. Due to strong curvatures of modern windshields, particularly the strong curvatures of windshields of rotary wing aircrafts, the cleaning performance of wiper blades is not continuous in all windshield areas. Especially towards the outer left or outer right side position the windshields of nowadays helicopters are strongly curved which leads to a poor cleaning performance in this area by using conventional wiper systems.
Lean angles α higher than 20° lead to very poor cleaning performance and moreover the frame holding the lip of the wiper blade touches the windshield and subsequently the bias of the lip of the wiper blade against the windshield is restricted. A further consequence of the frame touching the windshield is that the frame during operation may scratch the windshield.
The document EP0317767 describes a windshield wiper arrangement for curved surfaces. The arrangement has a retainer, a joint shaft pivotally coupled to the retainer about an axis, a wiper blade having a longitudinal axis and that is coupled to the joint shaft so that the longitudinal axis of the wiper blade is parallel to the axis of the joint shaft. A linkage allows driving the wiper blade across a surface to be wiped. The linkage comprises at least one steering arm and an extension mounted on the steering arm. The steering arm is pivotally coupled to the retainer. A universal joint has a lever that is attached to the joint shaft and the extension of the steering arm is slidably received in the universal joint so that the lever is positively locked to the linkage. The extension is free to move axially in the universal joint, whereby the wiper blade can be pivoted under constraint about the joint shaft in a plane radial to the surface to be wiped.
The document U.S. Pat. No. 5,502,866 or WO9205982 describes a windshield wiper arrangement for curved surfaces with a joint shaft, a retainer and a wiper blade coupled to the joint shaft so that a longitudinal axis is parallel to an axis of the joint shaft. A linkage for the wiper blade to be driven across the surface comprises at least one steering arm and an extension mounted thereon. The steering arm is pivotally coupled to the retainer and a universal joint with a lever is attached to the joint shaft. The extension is slidably received in the universal joint so that the lever is positively locked to the linkage. The extension is free to move axially in the universal joint, whereby the wiper blade can be pivoted under constraint about the joint shaft in a plane radial to the surface to be wiped.
The document WO2005095170 describes a wiper arm assembly for windshield wiper systems having one or more arms. At one end where a wiper blade is located, the arm has a wiper blade holder. The coupling to the arm enables the wiper to pivot about an axis running in a longitudinal direction of the blade and to pivot about the longitudinal direction in a controlled manner. An additional control arm orientates the wiper blade perpendicular to the vehicle window.
The document FR2988666 describes a wiper with a sweeping unit and a drive system. The sweeping unit includes a scraper and a cambered and notched carrying rod. A toothed wheel engages with the rod for reciprocating movement of the rod. A fixed cambered guide slides relative to the rod and guides the rod. The rod extends from a distal end toward a proximal end secured to the sweeping unit.
The document FR2746355 describes a windscreen wiper with a wiper arm. This arm is mounted on a wiper head unit, which allows the arm to pivot around a transverse axis. The transverse axis is roughly parallel to the general plane of the windscreen. The wiper head has a main body mounted at the upper end of a drive shaft. The body carries a link head, which is mounted to pivot around a longitudinal axis. The longitudinal axis is roughly parallel to the plane of the glass. A slide moves within the main body, under the control of a cam and as a function of the angular position of the wiper arm. The slider and the link head are connected together. The control rod acts along the longitudinal axis to cause the head to slide within a bore of the slider, so that as the slider moves under the control of the cam. Thus, the link head rotates according to the angular position of the wiper arm.
The documents FR2757815, EP0296081 and EP0351528 show wiper systems with control of the wiper blade lean angle α. An additional control arm or other mechanic control parts and/or piloting actuators for orienting the wiper blade perpendicular to the vehicle windshield are disclosed. Different windshields with different degrees of curvature necessitate different special control parts and/or piloting actuators according to said prior art resulting in a high number of different special control parts and/or piloting actuators respectively for small series at relatively high costs.
The document US2002/0056168 proposes a wiper system, able to orient the wiper blade perpendicular to the windshield, where the control of a local lean angle along the wiper blade by the twist of wiper blade is the objective of the system. The additional orientation control of the local angle along the blade is more expensive, heavier and more complex in realization.